Scientific Waterfowling

Recent waterfowl research may have practical applications for waterfowlers

By Wade Bourne

They're the quiet foot soldiers of conservation, seeking greater understanding of waterfowl and their biological needs. These men and women are North America's waterfowl scientists, who work for federal and state agencies, universities, and private conservation groups like Ducks Unlimited. Through scientific research, they unlock the secrets of how to manage waterfowl and their habitats more effectively for the good of these resources and the people who treasure them.

In the process, these researchers also discover many things that can benefit hunters, such as waterfowl migration patterns, food preferences, responses to weather, etc. Following are interviews with four preeminent waterfowl researchers. We can learn a lot from these experts, not only about how ducks react to their environment, but also how to apply this knowledge for better hunting success.

Cold Weather and Snow Cover Drive Mallard Migrations

Dr. Michael Schummer is a scientist with Long Point Waterfowl in Port Rowan, Ontario. Before migrating north to work in Canada, he conducted post-doctoral research at Mississippi State University with Dr. Rick Kaminski. Specifically, in 2008 and 2009, Schummer studied how weather affects mallard movements, and if the timing of mallard migrations had changed over the years. "Southern hunters were worried that mallards weren't showing up in the same numbers and as early as they once did. They also wondered if these changes were related to the weather, and if this trend was going to continue. We set out to answer those questions," Schummer says.

The first step was determining what causes mallards to migrate. "We developed a weather severity index for mallard migrations," he explains. "Using different combinations of temperature and snow depth data and waterfowl counts from Missouri conservation areas, we correlated changes in numbers of mallards with weather events to determine which conditions are most likely to push these ducks down the flyways.

"We learned that mallard migrations are affected mostly by a combination of weather conditions, specifically how cold it is, how many days in a row the average temperature stays below freezing, how deep the snow is, and how many consecutive days at least one inch of snow is on the ground," Schummer says.

"What it comes down to is this: when it gets cold and stays cold for a long time, ducks start burning up body fat reserves. Prolonged cold can also increase ice coverage on wetlands, which results in less food being available to mallards. Then, if there's snow covering their food in dry fields and they're having difficulty replenishing this lost energy, they reach a threshold that makes them migrate.

"By correlating duck numbers with weather conditions on the Missouri conservation areas, we came up with a weather severity index that would predict when ducks would move farther south. Then we calculated the weather severity index at 60 different weather stations in the Atlantic and Mississippi flyways from 1950 to 2011 to see if the severity of weather known to spur mallard migrations during fall had changed."

Schummer says the data suggests that there has been no long-term, sustained change in the weather severity index from 1950 to the present. "Granted, we have had strings of years with warmer or colder weather patterns," he adds. "For instance, we had more severe weather in the 1970s and 1980s, while we had a string of milder weather in the 1990s and 2000s. What many duck hunters in the southern states of the Mississippi Flyway remember are the 1970s and 1980s, when mallards seemed to come early and in good numbers nearly every year. However, to a mallard the 1990s and 2000s were some of the mildest fall seasons on record. But there were also several mild years in a row back in the 1950s, and the 1960s had a mixed bag of mild and severe winters. Few hunters can remember back that far, though.

"Overall, from 1950 to 2011 we haven't seen continually milder weather and later migrations with fewer mallards arriving on their Deep South wintering grounds. Instead, each year's migration appears to be dependent on the severity of that year's fall and winter weather. Yes, we will have cyclic ups and downs, and some cycles will be more severe than others. In years with cold fall and winter weather, the ducks will still come down as early and in as great numbers as before. But during the warm cycles they will probably come later."

So what's the application in all this for hunters? "They can watch the weather up the flyway and be able to predict fairly accurately when ducks will move south," Schummer says.

"We learned that other dabbling ducks besides mallards begin to move farther south when the daily average temperature approaches freezing. However, it often takes several more days of freezing temperatures and snow cover to push mallards south from northern and mid-latitude staging areas. You can watch temperatures and snow lines and predict fairly accurately when this will happen."

Locate Areas with a Combination of Food and Resting Habitat

Dr. Mark Petrie is director of conservation planning at Ducks Unlimited's Vancouver, Washington, office. Four years ago DU staff participated in a study led by Dan Buffett and others from DU Canada to track duck movements in the Puget Sound−Fraser River delta along the Washington−British Columbia border. Specifically, the study focused on ducks' use of estuaries in these areas.

"It was previously assumed that ducks used estuaries that were close to agricultural food sources more than estuaries that had natural foods but no ready access to agricultural zones," Petrie explains. "We wanted to see if this was true. If so, this would help us identify and conserve the estuaries of greatest importance to ducks that pass through or winter in these study areas.

"We radio-marked 200 northern pintails and American wigeon, and monitored their movements from when they arrived in October until they left in March. Our study verified the earlier belief that the estuaries in close proximity to agricultural foods held ducks for much longer periods of time than areas with estuaries only. In these latter areas the ducks left when natural food sources in the estuaries were depleted. But they hung around all winter long in areas where the combination of estuaries and agricultural food sources existed." (Wigeon foraged heavily on green grasses planted as winter cover crops in harvested agricultural fields, and pintails primarily consumed leftover potatoes and waste grain in harvested fields.)

What is the lesson here for duck hunters? The answer is obvious: areas with a combination of safe resting habitat and plentiful agricultural foods will attract more ducks and hold them longer than other areas.

Waterfowlers should scout as much as time allows to find this preferred combination of food and refuge. Find the groceries in close proximity to healthy wetland habitat where waterfowl can rest without being disturbed, and you'll likely find lots of ducks.

Track the Migration by Satellite and Computer

Dr. Andrew Raedeke is a waterfowl biologist at the Missouri Department of Conservation's Resource Science Center in Columbia. In 2008 he helped set up a duck tracking system called the Mallard Migration Observation Network. Its main purpose was to answer the question that has been asked by waterfowlers for generations: where are the ducks?

"In the mid-2000s, many hunters and wildlife professionals were wondering if migration patterns were changing and why some traditional wintering grounds were attracting fewer ducks than they used to. The Arkansas Game and Fish Commission had launched a satellite tracking study of mallards fitted with transmitters to follow their movements. We expanded this study to learn if these transmitter-fitted ducks were behaving like normal ducks (those without transmitters) and providing locational information that was reflective of the mallard population as a whole," Raedeke explains.

"We fitted 80 mallards with GPS transmitters and followed their movements. We also set up the Mallard Migration Observation Network to compare readings from our satellite mallards with actual in-the-field counts. We did this to test the accuracy of the satellite duck readings and to provide a better idea of where the ducks actually were."

The Mallard Migration Observation Network consists of 125 trained observers who conduct duck counts at locations throughout the Mississippi and Central flyways. "We asked each observer to provide us with a weekly numerical ranking for the status of the mallard migration at their site," Raedeke continues. "Then, using these rankings, we developed a migration map to show where mallards are concentrated and how the migration is progressing. We post this map on our Missouri Department of Conservation website (mdc.mo.gov) for the public to view, and update it weekly."

Raedeke says researchers have learned several things by comparing the satellite duck readings to data compiled through the Mallard Migration Observation Network. "One thing we have learned is that initially, ducks wearing transmitters were behaving differently than birds in the general population. Their movements weren't reflective of what was really happening in the wild. From this, we learned that when you put the transmitters on the birds is very important. Birds trapped in late winter or spring migrated more on par with the general population. Now we can take GPS readings from our transmitter ducks and plot their locations with fairly high confidence that their locations are reflective of the progress of the mallard migration," he says.

What applications can hunters make from this study? "Well, they can visit our website, view the map, and know if the peak of the mallard migration is still to the north of their hunting area or if it has passed them by. If the majority of the birds are still to the north and a good cold front blows through, hunters would probably have more success hunting bigger water where migrating ducks are more likely to show up first. But after the peak of the migration has passed, hunters may be better off hunting smaller, more secluded waters where hunter-wary ‘local' ducks hang out," he advises.

Raedeke adds that the migration map can help hunters decide when to flood habitat on hunting clubs and leases. "In the old days, hunters used to flood all their property before opening day. But now we know that it's better to progressively flood new food and habitat as the season wears on. So hunters can use the Mallard Migration Observation Network map to decide whether to flood or hold off peak flooding a little longer. Then, when the migration gets close to their hunting area, they can provide new water and fresh food at the most opportune time to attract the most ducks," he says.

Agricultural Practices Influence Waterfowl Distribution

Dr. Rick Kaminski is a professor of wildlife ecology and holder of the James C. Kennedy Endowed Chair in Waterfowl and Wetlands Conservation at Mississippi State University.

Kaminski has 30 years of experience in waterfowl habitat research, mainly in the Mississippi Alluvial Valley (MAV). In recent years, he has overseen extensive studies in the MAV on food availability for wintering ducks. Specifically, Kaminski and his colleagues have focused on the abundance of rice, corn, soybeans, and grain sorghum (milo), as well as on agricultural practices that affect the availability of waste grain for wintering waterfowl.

"Food energy is crucial for sustaining waterfowl populations. We've learned that if food availability on the wintering grounds decreases, it may impact the birds' survival and subsequent reproduction," Kaminski says. "This is the main premise behind habitat conservation on the wintering grounds. Waterfowl must obtain adequate nutrition to endure winter and to return to the breeding grounds in spring and have a strong reproductive effort."

Kaminski's research has revealed that changing modern farming practices have reduced the availability of agricultural foods for wintering waterfowl in many areas. "Most row crops nowadays are being planted earlier in spring and harvested earlier in fall, and much of the waste grain left in the field rots or sprouts during September and October, before the ducks arrive on their wintering grounds," Kaminski explains. "Other birds and rodents also get their share. Thus we should mitigate this loss, and we have evaluated several ways to do so.

"We've learned that in harvested rice fields, more waste grain remains if the stubble is left standing or burned instead of being rolled or disked after harvest. We've observed that mallard use is greatest in fields that are burned and then flooded. When flames meander randomly through a field, they remove stubble in patches and leave it intact elsewhere. Ducks are attracted to this mix of patchy stubble and water. Plus, burning can prevent waste grain from sprouting, but the seeds are still edible and nourishing to the birds." (Kaminski notes that burning is not allowed in certain areas because of air quality and aviation regulations, but is allowed in most of the MAV.)

Another management practice that provides more food for ducks is growing what Kaminski calls "grassy corn." In this practice, the rows are planted farther apart (about three feet) than standard corn crops, which allows more sunlight to stimulate growth of natural grasses and sedges between the rows. This grassy understory, in turn, produces moist-soil seeds, and after the field is flooded, aquatic invertebrates flourish in the flooded grass, providing wintering ducks with protein and other nutrients.

As Petrie discovered in the Pacific Northwest, Kaminski's research has also documented that the highest densities of mallards and other dabbling ducks in the MAV occur in areas with a combination of natural wetlands, where the birds can rest and find natural foods, and agricultural crops, which provide reliable foraging habitat. In the Mississippi Delta, Kaminski found that the ideal mix of habitat for wintering ducks consists of approximately 50 percent flooded cropland, 20 percent forested wetlands, 20 percent moist-soil wetlands, and 10 percent permanent wetlands (beaver ponds, rivers, sloughs, etc.). "The exact percentages are not known, but these results emphasize that a complex of multiple habitats attracts a greater abundance and diversity of ducks than single habitat types," he says.